The French midfielder moved to Merseyside from Manchester United in a £23.8m deal three months ago, and has impressed in his 10 appearances for the club so far.
He told Sky Sports News: "This club has ambition. They want to do great things and it has put a lot of confidence in me. I want Everton to reach the top and play in the Champions League. I'm just 27 and I want to do big things with this football club.
"That was the main thing for me, I wanted a club with ambition - not just to speak but to act on it. They brought good players last summer and they will bring good players this summer, they told me so. That's what made me want to come.
"And I knew the players who were here already, every time I played against Everton it was hard."
Everton are currently seventh in the Premier League table, with 54 points from their 32 games.